System and method for determining a steering angle for a vehicle and system and method for controlling a vehicle based on same

Abstract

A system for determining an angular position of a pair of steerable wheels of a vehicle having a plurality of wheels can include a yaw rate sensor, a pair of wheel speed sensors and a controller. The yaw rate sensor can be configured to output data representative of an angular velocity of the vehicle about a vertical axis of the vehicle. Each of the pair of wheel speed sensors can be configured to output data representative of a rotational velocity of a respective one of the plurality of wheels. The controller can be in electrical communication with each of the pair of wheel speed sensors and the yaw rate sensor. The controller can be configured to determine a first steering angle based on data received from the yaw rate sensor, to determine a second steering angle based on data received from the plurality of wheel speed sensors, and to select one of the first steering angle and the second steering angle for use in manipulating various vehicle parameters, including torque vectoring parameters, among other parameters.

What is claimed is: 
     
       1. A system for determining an angular position of a pair of steerable wheels of a vehicle having a plurality of wheels comprising:
 a steering angle sensor configured to output sensor angle data representative of a toe angle of the steerable pair of wheels, the steering angle sensor being a relative position sensor; 
 a yaw rate sensor configured to output data representative of an angular velocity of the vehicle about a vertical axis of the vehicle; 
 a pair of wheel speed sensors, wherein each wheel speed sensor is configured to output data representative of a rotational velocity of a respective one of the plurality of wheels; and 
 a controller in electrical communication with each of the pair of wheel speed sensors and the yaw rate sensor, one of the relative position sensor and the controller being configured to determine a neutral position of the relative position sensor such that the neutral position corresponds to a position of the relative position sensor when the vehicle travels along a substantially straight path, and the controller being configured to:
 determine a first steering angle based on data received from the plurality of wheel speed sensors; 
 determine a second steering angle based on data received from the yaw rate sensor; and 
 determine the angular position of the pair of steerable wheels to be one of the first steering angle and the second steering angle until one of the relative position sensor and the controller determines the neutral position. 
 
 
     
     
       2. The system for determining an angular position of a pair of steerable wheels of a vehicle according to  claim 1 , wherein the controller is configured to determine the angular position of the pair of steerable wheels to be one of the first steering angle and the second steering angle based on:
 a comparison of the first steering angle relative to the second steering angle; and 
 a comparison of a rate of change over time of the first steering angle relative to a rate of change over time of the second steering angle. 
 
     
     
       3. The system for determining an angular position of a pair of steerable wheels of a vehicle according to  claim 1 , wherein the controller is configured to determine the angular position of the pair of steerable wheels to be one of the first steering angle and the second steering angle by:
 determining a first rate of change of the first steering angle with respect to time; 
 determining a second rate of change of the second steering angle with respect to time; 
 selecting the first steering angle when the first steering angle is less than the second steering angle and the first rate of change is less than the second rate of change; 
 selecting the second steering angle when the second steering angle is less than the first steering angle and the second rate of change is less than the first rate of change; 
 selecting a previously selected one of the first steering angle and the second steering angle when the first steering angle is less than the second steering angle and the first rate of change is greater than or equal to the second rate; and 
 selecting a previously selected one of the first steering angle and the second steering angle when the first steering angle is greater than or equal to the second steering angle and the first rate of change is less than the second rate of change. 
 
     
     
       4. The system for determining an angular position of a pair of steerable wheels of a vehicle according to  claim 1 , wherein the controller is configured to
 determine whether the first steering angle is positive or negative, 
 determine whether the second steering angle is positive or negative, and 
 estimate the angular position of the pair of steerable wheels to be zero if the first steering angle is positive and the second steering angle is negative or if the first steering angle is negative and the second steering angle is positive. 
 
     
     
       5. The system for determining an angular position of a pair of steerable wheels of a vehicle according to  claim 1 , wherein the controller is configured to select the sensor angle data after the one of the relative position sensor and the controller determines the neutral position. 
     
     
       6. A method for determining a steering angle of a pair of steerable wheels of a vehicle having a plurality of wheels comprising:
 providing a relative position steering angle sensor; 
 determining a neutral position of the steering angle sensor, where the neutral position corresponds to a position of the steering angle sensor when the vehicle travels a substantially straight path; 
 determining a first steering angle based on rotational velocity data of the plurality of wheels; 
 determining a second steering angle based on a yaw rate of the vehicle; and 
 determining the steering angle of the pair of steerable wheels to be one of the first steering angle and the second steering angle during the determining a neutral position. 
 
     
     
       7. The method for determining a steering angle of a pair of steerable wheels of a vehicle according to  claim 6 , wherein the determining the steering angle of the pair of steerable wheels to be one of the first steering angle and the second steering angle includes,
 comparing the first steering angle relative to the second steering angle; and 
 comparing a rate of change with respect to time of the first steering angle relative to a rate of change with respect to time of the second steering angle. 
 
     
     
       8. The method for determining a steering angle of a pair of steerable wheels of a vehicle according to  claim 6 , wherein the determining the steering angle of the pair of steerable wheels to be one of the first steering angle and the second steering angle includes,
 determining a first rate of change of the first steering angle over time; 
 determining a second rate of change of the second steering angle over time; 
 selecting the first steering angle when the first steering angle is less than the second steering angle and the first rate of change is less than the second rate of change; 
 selecting the second steering angle when the second steering angle is less than the first steering angle and the second rate of change is less than the first rate of change; 
 selecting a previously selected one of the first steering angle and the second steering angle when the first steering angle is less than the second steering angle and the first rate of change is greater than or equal to the second rate of change; and 
 selecting a previously selected one of the first steering angle and the second steering angle when the first steering angle is greater than or equal to the second steering angle and the first rate of change is less than the second rate of change. 
 
     
     
       9. The method for determining a steering angle of a pair of steerable wheels of a vehicle according to  claim 6 , further comprising:
 determining whether the first steering angle is positive or negative; 
 determining whether the second steering angle is positive or negative; and 
 estimating the angular position of the pair of steerable wheels to be zero if the first steering angle is positive and the second steering angle is negative or if the first steering angle is negative and the second steering angle is positive. 
 
     
     
       10. The method for determining a steering angle of a pair of steerable wheels of a vehicle according to  claim 6 , further comprising:
 selecting data from the relative position steering angle sensor after the determining a neutral position. 
 
     
     
       11. A control system for an all-wheel drive powertrain of a vehicle having a power source configured to produce torque, a steerable pair of wheels configured to be driven by the torque, and a second pair of wheels configured to be selectively driven by the torque, the control system comprising:
 a first clutch assembly selectively connecting a first wheel of the second pair of wheels to the power source; and 
 a second clutch assembly selectively connecting a second wheel of the second pair of wheels to the power source; 
 a relative position steering angle sensor configured to output sensor angle data representative of a toe angle of the steerable pair of wheels, 
 a yaw rate sensor configured to output data representative of an angular velocity of the vehicle about a vertical axis of the vehicle; 
 a pair of wheel speed sensors, wherein each wheel speed sensor is configured to output data representative of a rotational velocity of a respective one of the second pair of wheels; and 
 a controller in electrical communication with each of the plurality of wheel speed sensors and the yaw rate sensor, one of the relative position steering angle sensor and the controller being configured to determine a neutral position of the relative position steering angle sensor such that the neutral position corresponds to a position of the relative position steering angle sensor when the vehicle travels a substantially straight path, and the controller being configured to,
 determine a first steering angle based on data received from the plurality of wheel speed sensors; 
 determine a second steering angle based on data received from the yaw rate sensor; 
 determine an angular position of the steerable pair of wheels to be one of the first steering angle and the second steering angle until the one of the relative position steering angle sensor and the controller has determined the neutral position; and 
 modulate the clutch assemblies based on the angular position of the steerable pair of wheels to vary transmission of torque from the power source to the second pair of wheels. 
 
 
     
     
       12. The control system for an all-wheel drive powertrain of a vehicle according to  claim 11 , wherein the controller is configured to select the sensor angle data after the one of the relative position steering angle sensor and the controller has determined the neutral position. 
     
     
       13. The control system for an all-wheel drive powertrain of a vehicle according to  claim 11 , wherein the controller is configured to determine the angular position of the steerable pair of wheels to be one of the first steering angle and the second steering angle by,
 determining a first rate of change of the first steering angle with respect to time, 
 determining a second rate of change of the second steering angle with respect to time, 
 selecting the first steering angle when the first steering angle is less than the second steering angle and the first rate of change is less than the second rate of change, 
 selecting the second steering angle when the second steering angle is less than the first steering angle and the second rate of change is less than the first rate of change, 
 selecting a previously selected one of the first steering angle and the second steering angle when the first steering angle is less than the second steering angle and the first rate of change is greater than or equal to the second rate of change, and 
 selecting a previously selected one of the first steering angle and the second steering angle when the first steering angle is greater than or equal to the second steering angle and the first rate of change is less than the second rate of change. 
 
     
     
       14. The control system for an all-wheel drive powertrain of a vehicle according to  claim 11 , wherein the controller is configured to,
 modulate the clutch assemblies equally such that each clutch assembly transfers an equal amount of torque to a respective one of the second pair of wheels, and 
 modulate each clutch assembly independently such that torque transferred by the first clutch assembly to the first wheel is greater than torque transferred by the second clutch assembly to the second wheel based on one of the angular position determined by the controller and the sensor angle data. 
 
     
     
       15. The control system for an all-wheel drive powertrain of a vehicle according to  claim 11 , further comprising:
 a vehicle speed sensor configured to output data representative of a travel velocity of the vehicle, 
 wherein the controller is configured to determine the first steering angle based on data received from the yaw rate sensor and the vehicle speed sensor. 
 
     
     
       16. The system for determining an angular position of a pair of steerable wheels of a vehicle according to  claim 11 , wherein the controller is configured to
 determine whether the first steering angle is positive or negative, 
 determine whether the second steering angle is positive or negative, and 
 estimate the angular position of the pair of steerable wheels to be zero if the first steering angle is positive and the second steering angle is negative or if the first steering angle is negative and the second steering angle is positive. 
 
     
     
       17. A method for controlling an on-demand all-wheel drive system of a vehicle to supplement an operator's input to the vehicle comprising:
 providing a power source, a pair of steerable wheels driven by the power source, a pair of rear wheels selectively driven by the power source, a pair of rear clutch assemblies selectively connecting a respective one of the pair of rear wheels to the power source, a yaw rate sensor configured to output data representative of an angular velocity of the vehicle about a vertical axis of the vehicle, and a pair of wheel speed sensors configured to output data representative of a rotational speed of a respective one of the pair of rear wheels; 
 providing a relative position steering angle sensor configured to output data representative of angular position of the pair of steerable wheels; 
 calibrating the relative position steering angle sensor; 
 determining a first steering angle based on the rotational speed data; 
 determining a second steering angle based on the data from the yaw rate sensor; and 
 determining the angular position of the pair of steerable wheels to be one of the first steering angle and the second steering angle during the calibrating. 
 
     
     
       18. The method for controlling an on-demand all-wheel drive system of a vehicle to supplement an operator's input to the vehicle according to  claim 17 , wherein the determining the angular position of the pair of steerable wheels includes,
 determining a first rate of change of the first steering angle over time, 
 determining a second rate of change of the second steering angle over time, 
 selecting the first steering angle when the first steering angle is less than the second steering angle and the first rate of change is less than the second rate of change, 
 selecting the second steering angle when the second steering angle is less than the first steering angle and the second rate of change is less than the first rate of change, 
 selecting a previously selected one of the first steering angle and the second steering angle when the first steering angle is less than the second steering angle and the first rate of change is greater than or equal to the second rate of change, and 
 selecting a previously selected one of the first steering angle and the second steering angle when the second steering angle is less than the first steering angle and the second rate of change is greater than or equal to the first rate of change. 
 
     
     
       19. The method for controlling an on-demand all-wheel drive system of a vehicle to supplement an operator's input to the vehicle according to  claim 17 , further comprising:
 selecting the angular position data after the calibrating. 
 
     
     
       20. The method for controlling an on-demand all-wheel drive system of a vehicle to supplement an operator's input to the vehicle according to  claim 19 , further comprising:
 modulating the rear clutch assemblies based on one of the determined angular position and the angular position data. 
 
     
     
       21. The method for controlling an on-demand all-wheel drive system of a vehicle to supplement an operator's input to the vehicle according to  claim 17 , further comprising:
 determining whether the first steering angle is positive or negative; 
 determining whether the second steering angle is positive or negative; and 
 estimating the angular position of the pair of steerable wheels to be zero if the first steering angle is positive and the second steering angle is negative or if the first steering angle is negative and the second steering angle is positive.